2x12" Alpine Type-R box

[MattODoom]

Hello everyone, first post here.

I have two Alpine SWR-1242D dual 4ohm subs. These are a mainstream SPL sub if you're not familiar (imagine most of you are).

I just ordered a OAudio 500w plate amp:
http://www.oaudio.com/500W_SUBAMP.html

and am putting together a box to house these. I was inspired by this thread:
http://www.diyaudio.com/forums/showthread/t-91576.html

The box that I have drawn up has 4.5cu ft for the woofers (net, before driver displacement), with a port which measures 3.5"x16"x28".

I got a rough plan for the port size from this page:
http://www.carstereo.com/help2/Articles.cfm?id=31

This is supposedly tuned to 28hz.

Im looking for advice as to whether the port is properly tuned to 28hz, and if 28hz is even a good level to tune to. This box will be used at our college house for parties which as you might guess, consist of mostly rap and hip-hop.

Simple rendering:
http://www.mattodoom.com/hosted/box1.jpg

Thanks!

 

[technofreak]

OK, here we go

This sub would be GREAT for a car.

But not so great for discos of any kind.

Reason - the sensitivity of this type of cab is around 89 dB, compared to 97...99 of that of a good 18" PA sub.

This means your sub needs about 10 times more power to reach the same levels as a PA sub! Or put it this way - outside of car cabin with your sub you'll get around 115 dB at one meter (SPL drops 6 dB with every doubling of distance)- I get about the same result with four 8" 40 W fullrangers that cost around 20€/pc. With 500 W PA sub you will get 125 dB - this is twice as loud! A double 18" box would take a kW and wouldn't be much more expensive than those overhyped (IMO) car speakers, and give you 130 dB, in open air. Now that's some serious bass.

But. If those drivers have similar T/S parameters to Eminence LAB12, then they're good candidates for horn loading, and that's another story - THEN you can get around 130 dB out of these. At the expense of more complicated box.

 

[zoranaudio]

Hi Bass-man's!
The real Bass is for the real Man's!
I agree with previous guy :This kind of box is only for the car or home listening or great for the surround dvd system, and not for PA disco sounding or bigger club's because the eff. of this woofers also reached about 90dB maximum.
Here what I made for my loud (hi fi) room listening.
I exploated them both for about 6 years without any problems(I should knock on wood now)

 

[zoranaudio]

This combinations of rubber surrounding woofer (Pioneer 12"), and B&C PA 15" woofer sound's great if Phase tuned O.K, You'll get the lowest spectar of Audio with Pioneer 12 " and get some fast and very tight (well defined ) bass from the B&C woofer with different box like in the picture!I feel the bass knocks right in My chest and stomack even I am working out with heavy weights up to 200 KG at raw bench!!!!

 

[MattODoom]

Thanks for your input guys!

The room that these subs will be in is a fairly small one, this isnt a club were talking about, but our house.

The whole reason that Im building the box is because I've had these drivers laying around for 2+ years. Therefor, I would just like to put them to good use.

Do you recommend making some changes to the box configuration to get more out of these?

 

[technofreak]

Yes! Make it a horn

What model are they exactly, and could you post their Thiele/Small parameters. So I can make some horn calculations... Just out of curiosity

 

[peanut123]

I actually am using one Alpine S-Type in a sealed 1.25 cubic foot box with a Bash 300w plate amp for my home theater sub. I have the crossover set @80hz and I can tell you from just listening to it on movies it is awesome. A computer generated graph can give you an idea of the frequency range that a speaker can play in but I have founf that if you tune it to your tastes, your fine. I know I will get some grief on that statement but in my years as an home theater installer, this is what I have found. Peoples ears tune diffrently and in my business it doesnt matter what a computer graph says, its what the customer says.

 

[MattODoom]

SWR-1242D

http://vault.alpine-usa.com/products/documents/OM_SWR-1242D.PDF

 

[littlemike]

Consider a tapped horn

Ever heard of a tapped horn?

These drivers look like they will work well in a tapped horn enclosure. A proper tapped horn is definitely bigger than 4.5 cubic feet (closer to 20 for both drivers), but will have usable frequency response into the teens and an efficiency that is equal to or slightly better than the ported enclosure.

Tons of information in the "Collaborative Tapped Horn Project" thread here.

 

[defwing]

I have been contemplating a tapped horn for my Alpine Type-R 12". I have been playing around in hornresp. I am after low/deep bass, I currently have the x-over set on <70Hz with 350W RMS @ 4ohm although has had 550W in the past. I was wondering what you guys could come up for tapped horn design wise for the following T/S's?

SWR-1221D(2x2ohm)
Fs 27Hz
Vas 58L
SD 467.59cm^2
Sensitivity 87Db
QMS 8.68
Qes .4
Qts 0.38
Le 2.41mH

Cheers,
James.

 

[aznboi3644]

I'm sure if the set is for parties with rap music the TH can be compromised with the low end cut out around 35-40Hz to make up for efficiency.

 

[TravisDigital]

the calculations you posted will work. the port may be a little off but it seemed to be close enough to 28hz it really depends on the TS.
The biggest problem you should run into with this box is being evicted. I got evicted for an oldschool kicker comp 15" also tuned to 28hz, It shook the washing machines in the laundry room next building over from my towne house.
If you go with the horn configuration it will surely be louder, and you can expect police at your parties!

 

[MattODoom]

the calculations you posted will work. the port may be a little off but it seemed to be close enough to 28hz it really depends on the TS.
The biggest problem you should run into with this box is being evicted. I got evicted for an oldschool kicker comp 15" also tuned to 28hz, It shook the washing machines in the laundry room next building over from my towne house.
If you go with the horn configuration it will surely be louder, and you can expect police at your parties!

We ended up making a "proof of concept" out of some 3/4" ply so we could mess around with the port geometry. Neither of us has any experience with tuning ports and so we wanted to get some experience before we cut into the $60 1" MDF.

It took me a week and a half to get the 1" MDF to start with, as I am in the northern penn. of michigan and it had to be special ordered. I only have one sheet, so that pretty much rules out building a TH.

We tried the port using the dimensions I had mentioned for a 28hz tune and then we took it apart and reconfigured it for supposedly a 35hz tune. I liked the 28hz a lot more, with the 35hz port the base lines of most of the music hit some crazy spl and seemed very out of proportion with the rest of the notes.

Is 28hz all that uncommonly low? or is that pretty reasonable?

Test Box (AKA: Ghetto Sub1):
http://mattodoom.com/hosted/101_0237.JPG

 

[TravisDigital]

We ended up making a "proof of concept" out of some 3/4" ply so we could mess around with the port geometry. Neither of us has any experience with tuning ports and so we wanted to get some experience before we cut into the $60 1" MDF.

It took me a week and a half to get the 1" MDF to start with, as I am in the northern penn. of michigan and it had to be special ordered. I only have one sheet, so that pretty much rules out building a TH.

We tried the port using the dimensions I had mentioned for a 28hz tune and then we took it apart and reconfigured it for supposedly a 35hz tune. I liked the 28hz a lot more, with the 35hz port the base lines of most of the music hit some crazy spl and seemed very out of proportion with the rest of the notes.

Is 28hz all that uncommonly low? or is that pretty reasonable?

Test Box (AKA: Ghetto Sub1):
http://mattodoom.com/hosted/101_0237.JPG

it might be a little low for 1 12" but for 2 it seems ok. I generally tune ports to the drivers fs, but I usually use 15"s which are most commonly 28hz or lower. The test box at 35hz is probably closer to the fs of some type r's. I don't think 28hz is that uncommon for a pair of high excursion 12"s , Try the happy medium at 30hz that should give you everything you're looking for.

 

[MattODoom]

The spec sheet says that the type Rs have a Free Air Resonance (Fs right?) of 29hz.

 

[TravisDigital]

If the fs is 29hz your original plans for 28hz should perform very well with these woofers.
You said you tried 28hz and liked it more right? Was it "proportionate" with other frequencies, or did that problem only occur with the 35hz port?
Wait a minute... you said the original plan was 1"mdf, but you're testing with 3/4ply, so did you adjust calculations for different size wood? I personally would have forgotten to adjust most likely, that's why I asked. So if you pulled a me and forgot, your test box would have a slightly larger inside volume. You wouldn't notice in the box, but the port would give/take a few hertz.

 

[GM]

I have been contemplating a tapped horn for my Alpine Type-R 12".

Not too shabby, 200W/2 ohms or 400 W/4 ohms, ~316.249 L, half space:

GM

 

[MattODoom]

If the fs is 29hz your original plans for 28hz should perform very well with these woofers.
You said you tried 28hz and liked it more right? Was it "proportionate" with other frequencies, or did that problem only occur with the 35hz port?
Wait a minute... you said the original plan was 1"mdf, but you're testing with 3/4ply, so did you adjust calculations for different size wood? I personally would have forgotten to adjust most likely, that's why I asked. So if you pulled a me and forgot, your test box would have a slightly larger inside volume. You wouldn't notice in the box, but the port would give/take a few hertz.

Yeah we did account for the dimensional differences in the construction material. The 28hz sounded much better I think, the 35hz hit really really hard at one note, and sounded lackluster at the others. Also, with some songs that hit really really low notes ("I Put On" for instance) the low end response was compromised.

We're going to lug this 1" MDF up to the woodshop at school and do it up real nice. I'll be sure to take pics, but it could be a week plus!

 

[defwing]

GM,

Could I bother you for the Input specs sheet on that please? I have spent the last few days playing in hornresp and understand it and tapped horns a bit better. I have got two good configs already but yours looks better,

My go at replicating it is

s1 114cm^2
s4 1000cm^2
l12 30cm
l23 530cm
l34 45cm

Although mine is closer to 125dB, must be something different or wrong with mine.

Thanks for your time,
James.

 

[GM]

Greets!

Yours looks fine, mine is larger so looks a bit 'fuller'. I assume that any big differences are due to mine being in 2 pi space and possibly you not inputting the driver correctly due to it being a dual VC.

Parallel and series VC sims will look different, but adding inductance and its associated series resistance to the series sim evens out the difference as shown, though all things considered, probably not worth the extra cost.

Parallel VCs:

GM